Cycles and OSL Render - Weird Seam
OSL Shading issue with Diffuse Roughness > 0



By dupilcate the Diffuse shader as in the node setup belowe an lowering the amount of the second Diffuse Roughness to something like .95 you should get the expected result.

There seems to be an issue in the usage of that parameter. It leads to strange behaviours. Note that if you don't double the node but just try to lower the Roughness of the Diffuse shader node, you'll need to set it lower than 0.5 to achieve the given result.





Notice that is not related with the use of the OSL script because it still happens even with default nodes...



..when the same scene, rendered with OSL Shading disabled, gives expected results.